Monday, May 28, 2012

In my article "Is Sugar Fattening?", I discussed a recent review paper on fructose, by Dr. John Sievenpiper and colleagues (1). It was the most recent of several review papers to conclude that fructose is probably not inherently fattening in humans, but that it can be fattening if it's consumed to excess, due to the added calories. Dr. Sievenpiper and colleagues have also written other papers addressing the metabolic effects of fructose, which appear to be fairly minor unless it's consumed to excess (2, 3, 4, 5). The senior author on these studies is Dr. David Jenkins at McMaster University. David Despain, a science and health writer who publishes a nice blog called Evolving Health, recently interviewed Dr. Sievenpiper about his work.

It's an interesting interview and very timely, due to the recent attention paid to fructose in the popular media. This has mostly been driven by a couple of high-profile individuals-- an issue they discuss in the interview. The interview, recent papers, and sessions at scientific conferences are part of an effort by researchers to push back against some of the less well founded claims that have received widespread attention lately.

Monday, May 21, 2012

Recently, Chris Kresser published a series on dietary salt (sodium chloride) and health (1). One of the issues he covered is the effect of salt on blood pressure. Most studies have shown a relatively weak relationship between salt intake and blood pressure. My position overall is that we're currently eating a lot more salt than at almost any point in our evolutionary history as a species, so I tend to favor a moderately low salt intake. However, there may be more important factors than salt when it comes to blood pressure, at least in the short term.

Thursday, May 17, 2012

In previous posts, I reviewed some of the evidence suggesting that human evolution has accelerated rapidly since the development of agriculture (and to some degree, before it). Europeans (and other lineages with a long history of agriculture) carry known genetic adaptations to the Neolithic diet, and there are probably many adaptations that have not yet been identified. In my final post in this series, I'll argue that although we've adapted, the adaptation is probably not complete, and we're left in a sort of genetic limbo between the Paleolithic and Neolithic state.

Recent Genetic Adaptations are Often Crude

It may at first seem strange, but many genes responsible for common genetic disorders show evidence of positive selection. In other words, the genes that cause these disorders were favored by evolution at some point because they presumably provided a survival advantage. For example, the sickle cell anemia gene protects against malaria, but if you inherit two copies of it, you end up with a serious and life-threatening disorder (1). The cystic fibrosis gene may have been selected to protect against one or more infectious diseases, but again if you get two copies of it, quality of life and lifespan are greatly curtailed (2, 3). Familial Mediterranean fever is a very common disorder in Mediterranean populations, involving painful inflammatory attacks of the digestive tract, and sometimes a deadly condition called amyloidosis. It shows evidence of positive selection and probably protected against intestinal disease due to the heightened inflammatory state it confers to the digestive tract (4, 5). Celiac disease, a severe autoimmune reaction to gluten found in some grains, may be a by-product of selection for protection against bacterial infection (6). Phenylketonuria also shows evidence of positive selection (7), and the list goes on. It's clear that a lot of our recent evolution was in response to new disease pressures, likely from increased population density, sendentism, and contact with domestic animals.

Monday, May 7, 2012

In previous posts, I described how Otzi was (at least in large part) a genetic descendant of Middle Eastern agriculturalists, rather than being purely descended from local hunter-gatherers who adopted agriculture in situ. I also reviewed evidence showing that modern Europeans are a genetic mixture of local European hunter-gatherers, incoming agricultural populations from the Middle East, neanderthals, and perhaps other groups. In this post, I'll describe the evidence for rapid human evolution since the end of the Paleolithic period, and research indicating that some of these changes are adaptations to the Neolithic (agricultural/horticultural/pastoral) diet.

Humans have Evolved Significantly Since the End of the Paleolithic

Evolution by natural selection leaves a distinct signature in the genome, and geneticists can detect this signature tens of thousands of years after the fact by comparing many genomes to one another. A landmark paper published in 2007 by Dr. John Hawks and colleagues showed that humans have been undergoing "extraordinarily rapid recent genetic evolution" over the last 40,000 years (1). Furthermore:

Saturday, May 5, 2012

Last October, I participated in a panel discussion organized by the Harvard Food Law Society in Boston. The panel included Drs. Walter Willett, David Ludwig, Robert Lustig, and myself, with Corby Kummer as moderator. Dr. Willett is the chair of the Harvard Department of Nutrition; Dr. Ludwig is a professor of nutrition and pediatrics at Harvard; Dr. Lustig is a professor of clinical pediatrics at UCSF; and Kummer is a food writer and senior editor for The Atlantic.

About Me

I'm a writer and science consultant with a background in neuroscience and obesity research. I have a BS in biochemistry and a PhD in neurobiology. I'm the author of "The Hungry Brain: Outsmarting the Instincts That Make Us Overeat".

Copyright 2008-2017

Please feel free to reproduce the contents of this blog, on the condition that you:

1) Attribute the work to me

2) Provide a link to the page where you found it

3) Do not use it for commercial purposes

Financial disclosure

I am a co-creator of the Ideal Weight Program, and I receive revenue from the sale of this program.

In addition, I am registered as an Amazon affiliate. I may receive a small commission on the sale of some of the books I review, or other products sold through Amazon.

Disclaimer

This blog is a compilation of my opinions. It's not advice; it's information that you can take or leave as you please. I don't intend it to replace professional medical consultation or treatment. Your health is in your own hands.